Maryadi's MV22B Osprey Rel2.0 released - Page 25
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1. Thanks Rob. That's what has been nagging me.

So a hover is 90 deg nacelles, less than 25 knots, i.e., zero knots forward motion and zero fpm vertical speed. So how does one transition to a (perfect) hover without triggering the VRS danger?

2. Originally Posted by expat
So how does one transition to a (perfect) hover without triggering the VRS danger?
First, please realise that any simulation model is a simplification of reality.
As are the VRS criteria I coded ; in reality, occurance of VRS depends on a lot of other factors: like wind, air-pressure, total aircraft weight, etc etc.
So the "hard" criteria I mentioned, are just "simplified averages".

But to answer your question on how-to avoid VRS danger when flying this Osprey model:
In the transition from normal flight to hover: slowly increase nacelles angle to lose airspeed, whilst increasing TrustControlLever ("throttle") sufficiently to compensate for lost winglift (due to decreasing airspeed) and too high descent rate.
So: avoid rapid altitude drops in the transition: first slow down, then land vertically.
Main thing is to understand WHY VRS occurs. the video that Maryadi referenced in the above post explains it clearly.

Note that a "perfect hover" is relative to the ground surface, so not necessarily at 90 degrees nacelles angle and/or zero airspeed.
It's a balance between pitch-attitude, nacelles angles and current head/tail wind.
Which IS modelled.

Rob

3. Very clear Rob, thanks. And outstanding job you've done on the modeling/coding. This is such a fun aircraft.

4. Originally Posted by expat
Very clear Rob, thanks. And outstanding job you've done on the modeling/coding. This is such a fun aircraft.
Yes, I agree ….
But my added codings would have been "void", without Maryadi's exceptional visual model, VC, basic flightdynamics, systems programming, etc etc .
Hope that's clear ...LoL

Rob

5. Yes an impressive team effort from you and Maryadi.

is it possible to get a rear gun modelled as seen in the attached video?

http://www.funker530.com/ramp-gunner/

7. Originally Posted by rcbarend
The exact, now programmed, criteria to activate VRS are:
- Nacelles rotation > 82 degrees.
AND
- Airspeed < 25 KNots
AND
- Verticalspeed < -1200 Feet/min

Rob
Hi Rob,

Not meaning to be picky, but I think there's a typo in your reply...

Shouldn't "- Verticalspeed < -1200 Feet/min" be "- Verticalspeed > -1200 Feet/min" ? (In other words: MORE than -1200 Feet/min and not LESS than -1200 Feet/min.)

8. Well, technically (maths), -1300 is inferior to -1200.
But your remark makes sense, because we're talking about speed in a given direction...

9. Originally Posted by Daube
Well, technically (maths), -1300 is inferior to -1200.
But your remark makes sense, because we're talking about speed in a given direction...
I see what you mean. But rate of descent is expressed as a minus quantity and, therefore as in your example, -1300 ft/min is faster than -1200 ft/min - as your second sentence says.

10. Originally Posted by jeansy

is it possible to get a rear gun modelled as seen in the attached video?

http://www.funker530.com/ramp-gunner/
yes, it possible. but if it only gun, I think it not quite good because no operator over there. I don't have people model with bone animation for realistic animation. Pilot figure is not my work.
in other side, I forbidden to create/make a copy any real living things.
if someone could provide free model with animation, it would big thanks.
at early plan I want to make some crew doing some stuff around Osprey

11. Originally Posted by freded
Hi Rob,

Not meaning to be picky, but I think there's a typo in your reply...

Shouldn't "- Verticalspeed < -1200 Feet/min" be "- Verticalspeed > -1200 Feet/min" ? (In other words: MORE than -1200 Feet/min and not LESS than -1200 Feet/min.)
no freded, Rob is correct.
verticalspeed is less than -1200 Feet/min the symbol is " < " to get -1300, -1400, -1500 and so on.

if
verticalspeed is more than - 1200 Feet/min the symbol you propose is " > " it get -1100, -1000, -900 and so on.

12. Well it is that interpretation I find confusing.

As we are not talking about a simple static dimension eg altitude: 1,200 ft is a "greater" altitude than 1,000 ft but rather a RATE, it comes across as somewhat contradictory to say a VS GREATER than - 1,200 fpm is eg -1,000 fpm when we also say a VS of -1,500 fpm is a FASTER VS than -1,200 fpm.

If ATC asks me to increase my rate of descent currently at -1,200 fpm I comply by flying at a greater, in other words, faster VS of eg -1,500 fpm.

13. Common life and computer math don't mix. +10 is greater than -20 in computer talk, and -20 is less than -10.

14. Originally Posted by expat
Well it is that interpretation I find confusing.

As we are not talking about a simple static dimension eg altitude: 1,200 ft is a "greater" altitude than 1,000 ft but rather a RATE, it comes across as somewhat contradictory to say a VS GREATER than - 1,200 fpm is eg -1,000 fpm when we also say a VS of -1,500 fpm is a FASTER VS than -1,200 fpm.

If ATC asks me to increase my rate of descent currently at -1,200 fpm I comply by flying at a greater, in other words, faster VS of eg -1,500 fpm.
Oh boy, I opened a can of worms apperantly ...LoL

… increase my rate of descent ,....

Right.
But then ATC speaks of "rate of descent" , not "vertical speed"
IMHO "rate of descent = +1500 fpm" is the same as "vertical speed = -1500 fpm"

Cheers, Rob

15. Well in aviation - and in this instance - the need to avoid a nasty fatal accident (the video of the VRS crash is nightmarish) it's the physics/kinematics that are relevant more than mathematical values.

So, to come back to the original question, do I want to avoid a VS of -2,0000 or -1,4000 to avoid VRS?
expect it's the former.

16. You want to avoid any VS more than -1200 FPM. So, -1300 fpm, -1400 FPM, -1555 FPM, and so on, are to be avoided. So yeah, -2000 fpm is just as bad a rate of descent as -1400 fpm is. Either one will (can?) lead to a VRS state, and a crash.

If it makes it easier, think of it in it's absolute value (modulus) form. |1200|, vs |-1400|. |-1400| is a greater absolute value. So is |1400|. When taking the absolute value, or modulus, the sign is discarded.

Think of it as being on a number line. Remember those from basic math? If you look along a number line, 3 is a farther away from the center point of it, or 0, than 2 is. Well, the modulus of -3 is too, because |-3| = 3. Again, farther away from 0 than 2 is, whatever the sign.
In fact, forget about the sign entirely. If your descending at 1200 FPM, your RATE is 1200 fpm. Going either direction, the rate of change is still 1200 fpm.

Ascending, VRS isn't a factor. Ascend as fast as you like. Have a rate of change of 3000 fpm if you want to. If your rate of change during descent, however, is 1300 fpm, you could encounter VRS.
Notice I didn't put a + or - in front of either number. I only spoke of rate of change, not a positive or negative number.

Rate of change of altitude, by the way, may also be called delta H, for change of height. Rate of change of any value, like height, or the plane's velocity, is commonly referred to as delta something. Delta V, delta H, whatever value you're discussing.

And that's it for today's math lesson, Your homework for tonight is...
Pat☺

17. Or just turn it off? It's very cool to have that functionally added to this amazing freeware model. So to recap, maintain a forward airspeed and do not exceed the set decent rate. For comparison purposes, a greater than 1500 fpm decent in the UH-60 is an autorotation basically. It's happens sometimes in helo formation landings to let lead land first and without knowing start to slow as you lose sight of lead (he's under the chin bubble somewhere). You also notice you are still way too high and try to get down quicker, without realizing you just connected the chain of elements required to put oneself into VRS. Remember the V-22 is better in airplane mode.

18. No Rob!
It may have been your can of worms - but I opened it!!

Still, with a little bit of luck (Quote from 'My Fair Lady') we'll all have learned from the subsequent discussion...

19. Originally Posted by freded
No Rob!
It may have been your can of worms - but I opened it!!

Still, with a little bit of luck (Quote from 'My Fair Lady') we'll all have learned from the subsequent discussion...
No worries ....LoL
I just realised that this is probably a classical example of mis-communication between a IT-designer (thinking in math/implementation terms) and an IT-user (thinking in application terms).
No "right" or "wrong" here; it depends on the perspective .....

Cheers, Rob

20. Originally Posted by rcbarend
No worries ....LoL
I just realised that this is probably a classical example of mis-communication between a IT-designer (thinking in math/implementation terms) and an IT-user (thinking in application terms).
No "right" or "wrong" here; it depends on the perspective .....
I always wonder if I have to pay more when buying with a discount of -50%, too

So I'll just set nacelles rotation to 82 degrees or less OR (logical OR, not XOR!) the rate of descent(!) below 1200fpm, then the VRS can't affect me (in the sim! I'm sure bad things can happen in the real thing even at 82 degrees).

21. It's a lovely plane. Amazing work! Thank you very much for this. Another milestone in an aging FSX.

I have one question though. How does the nacelle work in both Arm and Act mode? I can still control them when Act mode is active in which I thought it would be "locked" to auto. Thanks again.

Cheers

22. Originally Posted by Peg o my heart
It's a lovely plane. Amazing work! Thank you very much for this. Another milestone in an aging FSX.

I have one question though. How does the nacelle work in both Arm and Act mode? I can still control them when Act mode is active in which I thought it would be "locked" to auto. Thanks again.

Cheers

23. Originally Posted by Peg o my heart
It's a lovely plane. Amazing work! Thank you very much for this. Another milestone in an aging FSX.

I have one question though. How does the nacelle work in both Arm and Act mode? I can still control them when Act mode is active in which I thought it would be "locked" to auto. Thanks again.

Cheers
Yes, see page 18 like Maryadi says.
More specifically: section 6.1.3.1.14: AutoNac.

To elaborate a bit more:
With AutoNac Off, you can freely control the nacelles manually. (Except on the ground of course, where, with running engine(s), it's forced to min. 60 degrees).

With AutoNac ON ("ACT"), you can still move the nacelles manually.
But only within the limits specific by the Conversion corridor table. (on page 26)

The "Auto" also means that the nacelles are automatically moved to an angle within the limits specified by this table.
So if you are flying, and e.g. due to pitch attitude or TCL position the aircraft flies too fast for the actual nacelles position, the nacelles are auto-moved to a lower angle (dictated by the UpperAirspeedLimit in the graph).
Same if you fly too slow: the nacelles are auto-moved to a higher angle (dictated by the LowerAirspeedLimit in the graph).

In short: AutoNac ON means, that the automation will ensure, at any actual airspeed, that the nacelles angle will always be within the Upper and Lower limits.

Clear now ?

Rob

24. Originally Posted by rcbarend
Yes, see page 18 like Maryadi says.
More specifically: section 6.1.3.1.14: AutoNac.

To elaborate a bit more:
With AutoNac Off, you can freely control the nacelles manually. (Except on the ground of course, where, with running engine(s), it's forced to min. 60 degrees).

With AutoNac ON ("ACT"), you can still move the nacelles manually.
But only within the limits specific by the Conversion corridor table. (on page 26)

The "Auto" also means that the nacelles are automatically moved to an angle within the limits specified by this table.
So if you are flying, and e.g. due to pitch attitude or TCL position the aircraft flies too fast for the actual nacelles position, the nacelles are auto-moved to a lower angle (dictated by the UpperAirspeedLimit in the graph).
Same if you fly too slow: the nacelles are auto-moved to a higher angle (dictated by the LowerAirspeedLimit in the graph).

In short: AutoNac ON means, that the automation will ensure, at any actual airspeed, that the nacelles angle will always be within the Upper and Lower limits.

Clear now ?

Rob
As crystal..

Thank you very much Rob, got it now, and again this is an amazing work.

@Kalong. Siap. Will re read the manual again. Thank you.